gpx.studio/gpx/src/io.ts

import { XMLParser, XMLBuilder } from "fast-xml-parser";
import { GPXFileType } from "./types";
import { GPXFile } from "./gpx";

export function parseGPX(gpxData: string): GPXFile {
    const parser = new XMLParser({
        ignoreAttributes: false,
        attributeNamePrefix: "",
        attributesGroupName: 'attributes',
        isArray(name: string) {
            return name === 'trk' || name === 'trkseg' || name === 'trkpt' || name === 'wpt' || name === 'rte' || name === 'rtept' || name === 'gpxx:rpt';
        },
        attributeValueProcessor(attrName, attrValue, jPath) {
            if (attrName === 'lat' || attrName === 'lon') {
                return parseFloat(attrValue);
            }
            return attrValue;
        },
        transformTagName(tagName: string) {
            if (tagName === 'power') {
                // Transform the simple <power> tag to the more complex <gpxpx:PowerExtension> tag, the nested <gpxpx:PowerInWatts> tag is then handled by the tagValueProcessor
                return 'gpxpx:PowerExtension';
            }
            // Add the gpx_style namespace to the line style tags
            if (tagName === 'line') {
                return 'gpx_style:line';
            }
            if (tagName === 'color') {
                return 'gpx_style:color';
            }
            if (tagName === 'opacity') {
                return 'gpx_style:opacity';
            }
            if (tagName === 'width') {
                return 'gpx_style:width';
            }
            return tagName;
        },
        parseTagValue: false,
        tagValueProcessor(tagName, tagValue, jPath, hasAttributes, isLeafNode) {
            if (isLeafNode) {
                if (tagName === 'ele') {
                    return parseFloat(tagValue);
                }

                if (tagName === 'time') {
                    return new Date(tagValue);
                }

                if (tagName === 'gpxtpx:atemp' || tagName === 'gpxtpx:hr' || tagName === 'gpxtpx:cad' || tagName === 'gpxpx:PowerInWatts' ||
                    tagName === 'gpx_style:opacity' || tagName === 'gpx_style:width') {
                    return parseFloat(tagValue);
                }

                if (tagName === 'gpxpx:PowerExtension') {
                    // Finish the transformation of the simple <power> tag to the more complex <gpxpx:PowerExtension> tag
                    // Note that this only targets the transformed <power> tag, since it must be a leaf node
                    return {
                        'gpxpx:PowerInWatts': parseFloat(tagValue)
                    };
                }
            }

            return tagValue;
        },
    });

    const parsed: GPXFileType = parser.parse(gpxData).gpx;

    // @ts-ignore
    if (parsed.metadata === "") {
        parsed.metadata = {};
    }

    return new GPXFile(parsed);
}

export function buildGPX(file: GPXFile, exclude: string[]): string {
    const gpx = file.toGPXFileType(exclude);

    const builder = new XMLBuilder({
        format: true,
        ignoreAttributes: false,
        attributeNamePrefix: "",
        attributesGroupName: 'attributes',
        suppressEmptyNode: true,
        tagValueProcessor: (tagName: string, tagValue: unknown): string => {
            if (tagValue instanceof Date) {
                return tagValue.toISOString();
            }
            return tagValue.toString();
        },
    });

    gpx.attributes.creator = gpx.attributes.creator ?? 'https://gpx.studio';
    gpx.attributes['version'] = '1.1';
    gpx.attributes['xmlns'] = 'http://www.topografix.com/GPX/1/1';
    gpx.attributes['xmlns:xsi'] = 'http://www.w3.org/2001/XMLSchema-instance';
    gpx.attributes['xsi:schemaLocation'] = 'http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd http://www.garmin.com/xmlschemas/GpxExtensions/v3 http://www.garmin.com/xmlschemas/GpxExtensionsv3.xsd http://www.garmin.com/xmlschemas/TrackPointExtension/v1 http://www.garmin.com/xmlschemas/TrackPointExtensionv1.xsd http://www.garmin.com/xmlschemas/PowerExtension/v1 http://www.garmin.com/xmlschemas/PowerExtensionv1.xsd http://www.topografix.com/GPX/gpx_style/0/2 http://www.topografix.com/GPX/gpx_style/0/2/gpx_style.xsd';
    gpx.attributes['xmlns:gpxtpx'] = 'http://www.garmin.com/xmlschemas/TrackPointExtension/v1';
    gpx.attributes['xmlns:gpxx'] = 'http://www.garmin.com/xmlschemas/GpxExtensions/v3';
    gpx.attributes['xmlns:gpxpx'] = 'http://www.garmin.com/xmlschemas/PowerExtension/v1';
    gpx.attributes['xmlns:gpx_style'] = 'http://www.topografix.com/GPX/gpx_style/0/2';

    if (gpx.trk.length === 1 && (gpx.trk[0].name === undefined || gpx.trk[0].name === '')) {
        gpx.trk[0].name = gpx.metadata.name;
    }

    return builder.build({
        "?xml": {
            attributes: {
                version: "1.0",
                encoding: "UTF-8",
            }
        },
        gpx: removeEmptyElements(gpx)
    });
}

function removeEmptyElements(obj: GPXFileType): GPXFileType {
    for (const key in obj) {
        if (obj[key] === null || obj[key] === undefined || obj[key] === '' || (Array.isArray(obj[key]) && obj[key].length === 0)) {
            delete obj[key];
        } else if (typeof obj[key] === 'object' && !(obj[key] instanceof Date)) {
            removeEmptyElements(obj[key]);
            if (Object.keys(obj[key]).length === 0) {
                delete obj[key];
            }
        }
    }
    return obj;
}